An HIV-positive NHS specialist worker is fighting a landmark legal action that could prevent health authorities warning patients of potential exposure to the virus.

The worker is understood to claim his right to privacy supersedes the right to know of those he has treated, an argument which, if upheld in the high court, might have serious implications for the way the NHS handles such cases.

The worker, known as H, is said to argue that no patient traced in such cases in Britain has ever been found to be infected. There would therefore be no overwhelming public interest in the health authority concerned conducting such an exercise.

The worker won an injunction on Saturday from Mr Justice Scott Baker to stop the Mail on Sunday identifying him or the branch of medicine he works in, although the newspaper said he worked in a field that involved the routine wearing of rubber gloves to prevent infections transmitted.

The man has not practised since his diagnosis and says he has no plans to return to work. He argues that while the health authority will try to preserve his anonymity while contacting patients, his name is likely to come out. This would infringe his right to privacy under the 1998 Human Rights Act.

He is refusing to hand over records of his private patients, according to the Mail on Sunday. While he is obliged to disclose his NHS caseload, he does not consent to their records being used to notify them.

The health department agrees there has never been a known case of HIV being passed on by an infected healthcare worker to a patient in Britain, but there have been two abroad, in the US and France. The risk is considered "very small".

Lisa Power, of the Terrence Higgins Trust, which works with those infected with HIV, said: "Without knowing what area this specialist worked in, it is impossible to make a judgment about the risk." But she added that authorities tended to undertake very large exercises to trace patients who had probably not been at risk.

"They tend to do it to be 'better safe than sorry'. They don't want to be sued if they do make a mistake, and end up panicking a lot of people who have never been at risk."